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	$188.46	4.383%	$196.7202	$196.72	$196.70	$196.70
Purchase #2	$159.66	7.130%	$171.0438	$171.04	$171.05	$171.00
Purchase #3	$39.27	12.543%	$44.1956	$44.20	$44.20	$44.20
Purchase #4	$241.42	13.227%	$273.3526	$273.35	$273.35	$273.40
Purchase #5	$195.53	12.183%	$219.3514	$219.35	$219.35	$219.40
Purchase #6	$120.96	6.479%	$128.797	$128.80	$128.80	$128.80
Purchase #7	$101.49	4.247%	$105.8003	$105.80	$105.80	$105.80
7 purchase totals =	$1,046.79		$1,139.2609	$1,139.26	$1,139.25	$1,139.30