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	$106.40	8.785%	$115.7472	$115.75	$115.75	$115.70
Purchase #2	$19.25	8.464%	$20.8793	$20.88	$20.90	$20.90
Purchase #3	$89.43	11.648%	$99.8468	$99.85	$99.85	$99.80
Purchase #4	$63.34	13.104%	$71.6401	$71.64	$71.65	$71.60
Purchase #5	$53.55	6.151%	$56.8439	$56.84	$56.85	$56.80
Purchase #6	$106.79	11.229%	$118.7814	$118.78	$118.80	$118.80
Purchase #7	$73.51	8.375%	$79.6665	$79.67	$79.65	$79.70
7 purchase totals =	$512.27		$563.4052	$563.41	$563.45	$563.30