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	$127.77	11.158%	$142.0266	$142.03	$142.05	$142.00
Purchase #2	$219.95	6.346%	$233.908	$233.91	$233.90	$233.90
Purchase #3	$190.33	9.319%	$208.0669	$208.07	$208.05	$208.10
Purchase #4	$61.69	4.622%	$64.5413	$64.54	$64.55	$64.50
Purchase #5	$223.94	8.742%	$243.5168	$243.52	$243.50	$243.50
Purchase #6	$95.46	9.265%	$104.3044	$104.30	$104.30	$104.30
Purchase #7	$159.56	11.777%	$178.3514	$178.35	$178.35	$178.40
7 purchase totals =	$1,078.70		$1,174.7154	$1,174.72	$1,174.70	$1,174.70