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	$87.40	10.308%	$96.4092	$96.41	$96.40	$96.40
Purchase #2	$235.43	12.408%	$264.6422	$264.64	$264.65	$264.60
Purchase #3	$116.88	12.592%	$131.5975	$131.60	$131.60	$131.60
Purchase #4	$177.97	4.325%	$185.6672	$185.67	$185.65	$185.70
Purchase #5	$209.26	9.450%	$229.0351	$229.04	$229.05	$229.00
Purchase #6	$51.73	3.292%	$53.433	$53.43	$53.45	$53.40
Purchase #7	$47.54	6.200%	$50.4875	$50.49	$50.50	$50.50
7 purchase totals =	$926.21		$1,011.2717	$1,011.28	$1,011.30	$1,011.20