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	$90.37	6.376%	$96.132	$96.13	$96.15	$96.10
Purchase #2	$235.32	4.357%	$245.5729	$245.57	$245.55	$245.60
Purchase #3	$148.94	4.167%	$155.1463	$155.15	$155.15	$155.10
Purchase #4	$212.95	5.119%	$223.8509	$223.85	$223.85	$223.90
Purchase #5	$14.73	11.150%	$16.3724	$16.37	$16.35	$16.40
Purchase #6	$91.34	3.844%	$94.8511	$94.85	$94.85	$94.90
Purchase #7	$225.66	3.744%	$234.1087	$234.11	$234.10	$234.10
7 purchase totals =	$1,019.31		$1,066.0343	$1,066.03	$1,066.00	$1,066.10