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	$118.76	8.513%	$128.87	$128.87	$128.85	$128.90
Purchase #2	$39.85	6.510%	$42.4442	$42.44	$42.45	$42.40
Purchase #3	$13.29	8.687%	$14.4445	$14.44	$14.45	$14.40
Purchase #4	$223.86	4.478%	$233.8845	$233.88	$233.90	$233.90
Purchase #5	$196.88	6.223%	$209.1318	$209.13	$209.15	$209.10
Purchase #6	$72.41	13.682%	$82.3171	$82.32	$82.30	$82.30
Purchase #7	$32.28	4.782%	$33.8236	$33.82	$33.80	$33.80
7 purchase totals =	$697.33		$744.9157	$744.90	$744.90	$744.80