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	$102.33	7.480%	$109.9843	$109.98	$110.00	$110.00
Purchase #2	$59.25	6.189%	$62.917	$62.92	$62.90	$62.90
Purchase #3	$100.90	3.828%	$104.7625	$104.76	$104.75	$104.80
Purchase #4	$165.55	9.231%	$180.8319	$180.83	$180.85	$180.80
Purchase #5	$127.33	11.367%	$141.8036	$141.80	$141.80	$141.80
Purchase #6	$102.89	5.112%	$108.1497	$108.15	$108.15	$108.10
Purchase #7	$197.26	12.632%	$222.1779	$222.18	$222.20	$222.20
7 purchase totals =	$855.51		$930.6269	$930.62	$930.65	$930.60