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	$176.46	3.806%	$183.1761	$183.18	$183.20	$183.20
Purchase #2	$71.49	4.288%	$74.5555	$74.56	$74.55	$74.60
Purchase #3	$139.55	9.598%	$152.944	$152.94	$152.95	$152.90
Purchase #4	$124.51	9.728%	$136.6223	$136.62	$136.60	$136.60
Purchase #5	$82.27	3.472%	$85.1264	$85.13	$85.15	$85.10
Purchase #6	$141.30	13.586%	$160.497	$160.50	$160.50	$160.50
Purchase #7	$243.40	10.288%	$268.441	$268.44	$268.45	$268.40
7 purchase totals =	$978.98		$1,061.3623	$1,061.37	$1,061.40	$1,061.30