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	$29.91	7.312%	$32.097	$32.10	$32.10	$32.10
Purchase #2	$6.88	4.363%	$7.1802	$7.18	$7.20	$7.20
Purchase #3	$244.47	4.604%	$255.7254	$255.73	$255.75	$255.70
Purchase #4	$98.90	6.269%	$105.1	$105.10	$105.10	$105.10
Purchase #5	$53.36	10.625%	$59.0295	$59.03	$59.05	$59.00
Purchase #6	$147.47	5.469%	$155.5351	$155.54	$155.55	$155.50
Purchase #7	$229.36	5.678%	$242.3831	$242.38	$242.40	$242.40
7 purchase totals =	$810.35		$857.0503	$857.06	$857.15	$857.00