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	$56.55	8.717%	$61.4795	$61.48	$61.50	$61.50
Purchase #2	$80.70	11.138%	$89.6884	$89.69	$89.70	$89.70
Purchase #3	$149.57	6.219%	$158.8718	$158.87	$158.85	$158.90
Purchase #4	$234.87	11.704%	$262.3592	$262.36	$262.35	$262.40
Purchase #5	$226.39	8.345%	$245.2822	$245.28	$245.30	$245.30
Purchase #6	$65.87	5.417%	$69.4382	$69.44	$69.45	$69.40
Purchase #7	$196.85	13.680%	$223.7791	$223.78	$223.80	$223.80
7 purchase totals =	$1,010.80		$1,110.8984	$1,110.90	$1,110.95	$1,111.00