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	$53.86	11.226%	$59.9063	$59.91	$59.90	$59.90
Purchase #2	$64.86	12.711%	$73.1044	$73.10	$73.10	$73.10
Purchase #3	$193.77	8.617%	$210.4672	$210.47	$210.45	$210.50
Purchase #4	$245.71	7.655%	$264.5191	$264.52	$264.50	$264.50
Purchase #5	$192.46	6.472%	$204.916	$204.92	$204.90	$204.90
Purchase #6	$211.41	10.406%	$233.4093	$233.41	$233.40	$233.40
Purchase #7	$170.44	5.796%	$180.3187	$180.32	$180.30	$180.30
7 purchase totals =	$1,132.51		$1,226.6410	$1,226.65	$1,226.55	$1,226.60