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	$234.56	9.298%	$256.3694	$256.37	$256.35	$256.40
Purchase #2	$40.65	6.458%	$43.2752	$43.28	$43.30	$43.30
Purchase #3	$166.74	12.152%	$187.0022	$187.00	$187.00	$187.00
Purchase #4	$128.90	3.741%	$133.7221	$133.72	$133.70	$133.70
Purchase #5	$59.53	4.327%	$62.1059	$62.11	$62.10	$62.10
Purchase #6	$245.43	7.720%	$264.3772	$264.38	$264.40	$264.40
Purchase #7	$99.93	9.279%	$109.2025	$109.20	$109.20	$109.20
7 purchase totals =	$975.74		$1,056.0545	$1,056.06	$1,056.05	$1,056.10