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	$218.29	9.254%	$238.4906	$238.49	$238.50	$238.50
Purchase #2	$96.95	13.147%	$109.696	$109.70	$109.70	$109.70
Purchase #3	$86.69	4.668%	$90.7367	$90.74	$90.75	$90.70
Purchase #4	$214.52	4.180%	$223.4869	$223.49	$223.50	$223.50
Purchase #5	$186.35	5.350%	$196.3197	$196.32	$196.30	$196.30
Purchase #6	$217.67	12.740%	$245.4012	$245.40	$245.40	$245.40
Purchase #7	$190.47	9.793%	$209.1227	$209.12	$209.10	$209.10
7 purchase totals =	$1,210.94		$1,313.2538	$1,313.26	$1,313.25	$1,313.20