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	$93.52	4.847%	$98.0529	$98.05	$98.05	$98.10
Purchase #2	$181.32	4.329%	$189.1693	$189.17	$189.15	$189.20
Purchase #3	$114.53	8.420%	$124.1734	$124.17	$124.15	$124.20
Purchase #4	$69.53	4.694%	$72.7937	$72.79	$72.80	$72.80
Purchase #5	$88.88	3.586%	$92.0672	$92.07	$92.05	$92.10
Purchase #6	$215.84	13.673%	$245.3518	$245.35	$245.35	$245.40
Purchase #7	$96.83	3.591%	$100.3072	$100.31	$100.30	$100.30
7 purchase totals =	$860.45		$921.9155	$921.91	$921.85	$922.10