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	$94.69	3.844%	$98.3299	$98.33	$98.35	$98.30
Purchase #2	$133.35	12.812%	$150.4348	$150.43	$150.45	$150.40
Purchase #3	$191.90	4.317%	$200.1843	$200.18	$200.20	$200.20
Purchase #4	$99.45	11.469%	$110.8559	$110.86	$110.85	$110.90
Purchase #5	$87.80	3.215%	$90.6228	$90.62	$90.60	$90.60
Purchase #6	$168.38	8.798%	$183.1941	$183.19	$183.20	$183.20
Purchase #7	$53.26	9.827%	$58.4939	$58.49	$58.50	$58.50
7 purchase totals =	$828.83		$892.1157	$892.10	$892.15	$892.10