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	$144.42	13.573%	$164.0221	$164.02	$164.00	$164.00
Purchase #2	$68.26	9.723%	$74.8969	$74.90	$74.90	$74.90
Purchase #3	$242.47	11.728%	$270.9069	$270.91	$270.90	$270.90
Purchase #4	$194.63	5.487%	$205.3093	$205.31	$205.30	$205.30
Purchase #5	$30.39	9.642%	$33.3202	$33.32	$33.30	$33.30
Purchase #6	$50.34	5.543%	$53.1303	$53.13	$53.15	$53.10
Purchase #7	$202.52	9.837%	$222.4419	$222.44	$222.45	$222.40
7 purchase totals =	$933.03		$1,024.0276	$1,024.03	$1,024.00	$1,023.90