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	$91.99	4.500%	$96.1296	$96.13	$96.15	$96.10
Purchase #2	$115.50	4.684%	$120.91	$120.91	$120.90	$120.90
Purchase #3	$40.59	12.793%	$45.7827	$45.78	$45.80	$45.80
Purchase #4	$228.84	8.501%	$248.2937	$248.29	$248.30	$248.30
Purchase #5	$222.59	11.803%	$248.8623	$248.86	$248.85	$248.90
Purchase #6	$55.32	12.383%	$62.1703	$62.17	$62.15	$62.20
Purchase #7	$175.33	10.745%	$194.1692	$194.17	$194.15	$194.20
7 purchase totals =	$930.16		$1,016.3178	$1,016.31	$1,016.30	$1,016.40