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	$99.52	9.583%	$109.057	$109.06	$109.05	$109.10
Purchase #2	$85.86	12.865%	$96.9059	$96.91	$96.90	$96.90
Purchase #3	$203.37	13.354%	$230.528	$230.53	$230.55	$230.50
Purchase #4	$222.26	10.453%	$245.4928	$245.49	$245.50	$245.50
Purchase #5	$53.54	3.314%	$55.3143	$55.31	$55.30	$55.30
Purchase #6	$237.39	7.191%	$254.4607	$254.46	$254.45	$254.50
Purchase #7	$103.51	8.719%	$112.535	$112.54	$112.55	$112.50
7 purchase totals =	$1,005.45		$1,104.2937	$1,104.30	$1,104.30	$1,104.30