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	$174.67	6.237%	$185.5642	$185.56	$185.55	$185.60
Purchase #2	$239.86	13.399%	$271.9988	$272.00	$272.00	$272.00
Purchase #3	$96.56	4.797%	$101.192	$101.19	$101.20	$101.20
Purchase #4	$75.93	12.560%	$85.4668	$85.47	$85.45	$85.50
Purchase #5	$77.90	5.641%	$82.2943	$82.29	$82.30	$82.30
Purchase #6	$178.62	4.853%	$187.2884	$187.29	$187.30	$187.30
Purchase #7	$94.38	4.572%	$98.6951	$98.70	$98.70	$98.70
7 purchase totals =	$937.92		$1,012.4996	$1,012.50	$1,012.50	$1,012.60