Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$235.55	7.872%	$254.0925	$254.09	$254.10	$254.10
Purchase #2	$123.92	6.202%	$131.6055	$131.61	$131.60	$131.60
Purchase #3	$182.57	3.460%	$188.8869	$188.89	$188.90	$188.90
Purchase #4	$160.44	13.104%	$181.4641	$181.46	$181.45	$181.50
Purchase #5	$115.68	3.653%	$119.9058	$119.91	$119.90	$119.90
Purchase #6	$105.30	5.309%	$110.8904	$110.89	$110.90	$110.90
Purchase #7	$172.87	3.271%	$178.5246	$178.52	$178.50	$178.50
7 purchase totals =	$1,096.33		$1,165.3698	$1,165.37	$1,165.35	$1,165.40