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	$202.52	5.686%	$214.0353	$214.04	$214.05	$214.00
Purchase #2	$59.90	7.536%	$64.4141	$64.41	$64.40	$64.40
Purchase #3	$79.65	12.108%	$89.294	$89.29	$89.30	$89.30
Purchase #4	$159.32	12.393%	$179.0645	$179.06	$179.05	$179.10
Purchase #5	$234.45	12.552%	$263.8782	$263.88	$263.90	$263.90
Purchase #6	$206.90	7.399%	$222.2085	$222.21	$222.20	$222.20
Purchase #7	$160.81	5.608%	$169.8282	$169.83	$169.85	$169.80
7 purchase totals =	$1,103.55		$1,202.7228	$1,202.72	$1,202.75	$1,202.70