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	$165.59	7.545%	$178.0838	$178.08	$178.10	$178.10
Purchase #2	$52.73	9.280%	$57.6233	$57.62	$57.60	$57.60
Purchase #3	$242.69	11.373%	$270.2911	$270.29	$270.30	$270.30
Purchase #4	$9.59	7.763%	$10.3345	$10.33	$10.35	$10.30
Purchase #5	$172.60	13.739%	$196.3135	$196.31	$196.30	$196.30
Purchase #6	$202.78	11.107%	$225.3028	$225.30	$225.30	$225.30
Purchase #7	$86.96	9.703%	$95.3977	$95.40	$95.40	$95.40
7 purchase totals =	$932.94		$1,033.3467	$1,033.33	$1,033.35	$1,033.30