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	$153.50	9.801%	$168.5445	$168.54	$168.55	$168.50
Purchase #2	$40.49	3.504%	$41.9088	$41.91	$41.90	$41.90
Purchase #3	$169.43	11.182%	$188.3757	$188.38	$188.40	$188.40
Purchase #4	$181.31	3.401%	$187.4764	$187.48	$187.50	$187.50
Purchase #5	$250.34	6.475%	$266.5495	$266.55	$266.55	$266.50
Purchase #6	$96.32	11.428%	$107.3274	$107.33	$107.35	$107.30
Purchase #7	$206.56	8.171%	$223.438	$223.44	$223.45	$223.40
7 purchase totals =	$1,097.95		$1,183.6203	$1,183.63	$1,183.70	$1,183.50