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	$50.58	4.498%	$52.8551	$52.86	$52.85	$52.90
Purchase #2	$203.27	3.598%	$210.5837	$210.58	$210.60	$210.60
Purchase #3	$67.42	7.661%	$72.585	$72.59	$72.60	$72.60
Purchase #4	$115.54	6.774%	$123.3667	$123.37	$123.35	$123.40
Purchase #5	$184.33	3.676%	$191.106	$191.11	$191.10	$191.10
Purchase #6	$243.46	4.563%	$254.5691	$254.57	$254.55	$254.60
Purchase #7	$22.91	12.857%	$25.8555	$25.86	$25.85	$25.90
7 purchase totals =	$887.51		$930.9211	$930.94	$930.90	$931.10