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	$241.97	9.148%	$264.1054	$264.11	$264.10	$264.10
Purchase #2	$28.33	5.502%	$29.8887	$29.89	$29.90	$29.90
Purchase #3	$157.75	3.115%	$162.6639	$162.66	$162.65	$162.70
Purchase #4	$137.65	4.709%	$144.1319	$144.13	$144.15	$144.10
Purchase #5	$204.69	5.169%	$215.2704	$215.27	$215.25	$215.30
Purchase #6	$55.27	9.179%	$60.3432	$60.34	$60.35	$60.30
Purchase #7	$178.61	6.688%	$190.5554	$190.56	$190.55	$190.60
7 purchase totals =	$1,004.27		$1,066.9589	$1,066.96	$1,066.95	$1,067.00