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	$188.81	6.113%	$200.352	$200.35	$200.35	$200.40
Purchase #2	$58.83	3.385%	$60.8214	$60.82	$60.80	$60.80
Purchase #3	$155.82	4.180%	$162.3333	$162.33	$162.35	$162.30
Purchase #4	$110.78	10.834%	$122.7819	$122.78	$122.80	$122.80
Purchase #5	$210.32	10.271%	$231.922	$231.92	$231.90	$231.90
Purchase #6	$168.32	10.747%	$186.4094	$186.41	$186.40	$186.40
Purchase #7	$178.94	4.459%	$186.9189	$186.92	$186.90	$186.90
7 purchase totals =	$1,071.82		$1,151.5389	$1,151.53	$1,151.50	$1,151.50