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	$173.28	10.370%	$191.2491	$191.25	$191.25	$191.20
Purchase #2	$173.76	10.650%	$192.2654	$192.27	$192.25	$192.30
Purchase #3	$184.51	8.154%	$199.5549	$199.55	$199.55	$199.60
Purchase #4	$193.27	6.234%	$205.3185	$205.32	$205.30	$205.30
Purchase #5	$41.91	10.236%	$46.1999	$46.20	$46.20	$46.20
Purchase #6	$71.89	12.786%	$81.0819	$81.08	$81.10	$81.10
Purchase #7	$172.44	13.711%	$196.0832	$196.08	$196.10	$196.10
7 purchase totals =	$1,011.06		$1,111.7529	$1,111.75	$1,111.75	$1,111.80