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	$167.98	10.524%	$185.6582	$185.66	$185.65	$185.70
Purchase #2	$202.89	3.240%	$209.4636	$209.46	$209.45	$209.50
Purchase #3	$118.44	4.851%	$124.1855	$124.19	$124.20	$124.20
Purchase #4	$169.89	11.687%	$189.745	$189.75	$189.75	$189.70
Purchase #5	$201.90	5.238%	$212.4755	$212.48	$212.50	$212.50
Purchase #6	$103.51	4.860%	$108.5406	$108.54	$108.55	$108.50
Purchase #7	$196.28	7.707%	$211.4073	$211.41	$211.40	$211.40
7 purchase totals =	$1,160.89		$1,241.4757	$1,241.49	$1,241.50	$1,241.50