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	$148.54	3.786%	$154.1637	$154.16	$154.15	$154.20
Purchase #2	$221.64	6.403%	$235.8316	$235.83	$235.85	$235.80
Purchase #3	$144.58	7.711%	$155.7286	$155.73	$155.75	$155.70
Purchase #4	$67.80	6.802%	$72.4118	$72.41	$72.40	$72.40
Purchase #5	$102.62	3.116%	$105.8176	$105.82	$105.80	$105.80
Purchase #6	$216.29	11.629%	$241.4424	$241.44	$241.45	$241.40
Purchase #7	$119.35	10.539%	$131.9283	$131.93	$131.95	$131.90
7 purchase totals =	$1,020.82		$1,097.3240	$1,097.32	$1,097.35	$1,097.20