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	$99.88	6.236%	$106.1085	$106.11	$106.10	$106.10
Purchase #2	$207.36	11.457%	$231.1172	$231.12	$231.10	$231.10
Purchase #3	$243.37	11.512%	$271.3868	$271.39	$271.40	$271.40
Purchase #4	$216.33	11.234%	$240.6325	$240.63	$240.65	$240.60
Purchase #5	$112.64	13.107%	$127.4037	$127.40	$127.40	$127.40
Purchase #6	$54.93	11.769%	$61.3947	$61.39	$61.40	$61.40
Purchase #7	$39.90	9.645%	$43.7484	$43.75	$43.75	$43.70
7 purchase totals =	$974.41		$1,081.7918	$1,081.79	$1,081.80	$1,081.70