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	$107.56	9.616%	$117.903	$117.90	$117.90	$117.90
Purchase #2	$245.56	12.356%	$275.9014	$275.90	$275.90	$275.90
Purchase #3	$120.80	5.274%	$127.171	$127.17	$127.15	$127.20
Purchase #4	$50.53	3.202%	$52.148	$52.15	$52.15	$52.10
Purchase #5	$148.91	12.511%	$167.5401	$167.54	$167.55	$167.50
Purchase #6	$171.81	8.736%	$186.8193	$186.82	$186.80	$186.80
Purchase #7	$222.62	5.596%	$235.0778	$235.08	$235.10	$235.10
7 purchase totals =	$1,067.79		$1,162.5606	$1,162.56	$1,162.55	$1,162.50