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	$189.54	5.119%	$199.2426	$199.24	$199.25	$199.20
Purchase #2	$54.99	4.862%	$57.6636	$57.66	$57.65	$57.70
Purchase #3	$86.79	3.578%	$89.8953	$89.90	$89.90	$89.90
Purchase #4	$243.74	11.727%	$272.3234	$272.32	$272.30	$272.30
Purchase #5	$215.84	7.207%	$231.3956	$231.40	$231.40	$231.40
Purchase #6	$91.74	10.690%	$101.547	$101.55	$101.55	$101.50
Purchase #7	$164.76	4.592%	$172.3258	$172.33	$172.35	$172.30
7 purchase totals =	$1,047.40		$1,124.3933	$1,124.40	$1,124.40	$1,124.30