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	$85.50	4.861%	$89.6562	$89.66	$89.65	$89.70
Purchase #2	$91.71	12.424%	$103.1041	$103.10	$103.10	$103.10
Purchase #3	$247.74	7.278%	$265.7705	$265.77	$265.75	$265.80
Purchase #4	$186.98	4.851%	$196.0504	$196.05	$196.05	$196.10
Purchase #5	$98.78	4.817%	$103.5382	$103.54	$103.55	$103.50
Purchase #6	$229.38	5.610%	$242.2482	$242.25	$242.25	$242.20
Purchase #7	$149.93	3.732%	$155.5254	$155.53	$155.55	$155.50
7 purchase totals =	$1,090.02		$1,155.8930	$1,155.90	$1,155.90	$1,155.90