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	$62.31	4.590%	$65.17	$65.17	$65.15	$65.20
Purchase #2	$128.89	10.792%	$142.7998	$142.80	$142.80	$142.80
Purchase #3	$47.51	10.475%	$52.4867	$52.49	$52.50	$52.50
Purchase #4	$96.69	8.514%	$104.9222	$104.92	$104.90	$104.90
Purchase #5	$33.80	11.336%	$37.6316	$37.63	$37.65	$37.60
Purchase #6	$74.48	6.231%	$79.1208	$79.12	$79.10	$79.10
Purchase #7	$144.97	3.557%	$150.1266	$150.13	$150.15	$150.10
7 purchase totals =	$588.65		$632.2577	$632.26	$632.25	$632.20