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	$130.96	7.757%	$141.1186	$141.12	$141.10	$141.10
Purchase #2	$79.65	10.834%	$88.2793	$88.28	$88.30	$88.30
Purchase #3	$30.73	3.550%	$31.8209	$31.82	$31.80	$31.80
Purchase #4	$204.61	5.543%	$215.9515	$215.95	$215.95	$216.00
Purchase #5	$79.67	10.492%	$88.029	$88.03	$88.05	$88.00
Purchase #6	$175.97	11.464%	$196.1432	$196.14	$196.15	$196.10
Purchase #7	$163.92	3.601%	$169.8228	$169.82	$169.80	$169.80
7 purchase totals =	$865.51		$931.1653	$931.16	$931.15	$931.10