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	$95.65	8.637%	$103.9113	$103.91	$103.90	$103.90
Purchase #2	$77.85	7.559%	$83.7347	$83.73	$83.75	$83.70
Purchase #3	$244.31	8.116%	$264.1382	$264.14	$264.15	$264.10
Purchase #4	$170.40	6.255%	$181.0585	$181.06	$181.05	$181.10
Purchase #5	$129.35	9.855%	$142.0974	$142.10	$142.10	$142.10
Purchase #6	$105.89	9.845%	$116.3149	$116.31	$116.30	$116.30
Purchase #7	$54.73	9.131%	$59.7274	$59.73	$59.75	$59.70
7 purchase totals =	$878.18		$950.9824	$950.98	$951.00	$950.90