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	$156.47	9.289%	$171.0045	$171.00	$171.00	$171.00
Purchase #2	$184.84	7.361%	$198.4461	$198.45	$198.45	$198.40
Purchase #3	$56.80	9.128%	$61.9847	$61.98	$62.00	$62.00
Purchase #4	$39.70	7.195%	$42.5564	$42.56	$42.55	$42.60
Purchase #5	$133.72	10.271%	$147.4544	$147.45	$147.45	$147.50
Purchase #6	$142.64	6.494%	$151.903	$151.90	$151.90	$151.90
Purchase #7	$218.28	9.418%	$238.8376	$238.84	$238.85	$238.80
7 purchase totals =	$932.45		$1,012.1867	$1,012.18	$1,012.20	$1,012.20