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	$96.48	4.801%	$101.112	$101.11	$101.10	$101.10
Purchase #2	$104.50	5.191%	$109.9246	$109.92	$109.90	$109.90
Purchase #3	$110.59	13.309%	$125.3084	$125.31	$125.30	$125.30
Purchase #4	$63.69	12.318%	$71.5353	$71.54	$71.55	$71.50
Purchase #5	$236.48	10.555%	$261.4405	$261.44	$261.45	$261.40
Purchase #6	$74.31	9.426%	$81.3145	$81.31	$81.30	$81.30
Purchase #7	$195.61	13.552%	$222.1191	$222.12	$222.10	$222.10
7 purchase totals =	$881.66		$972.7544	$972.75	$972.70	$972.60