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	$85.97	3.649%	$89.107	$89.11	$89.10	$89.10
Purchase #2	$111.54	12.118%	$125.0564	$125.06	$125.05	$125.10
Purchase #3	$22.34	13.163%	$25.2806	$25.28	$25.30	$25.30
Purchase #4	$225.55	8.770%	$245.3307	$245.33	$245.35	$245.30
Purchase #5	$41.51	3.372%	$42.9097	$42.91	$42.90	$42.90
Purchase #6	$241.93	10.596%	$267.5649	$267.56	$267.55	$267.60
Purchase #7	$210.43	6.540%	$224.1921	$224.19	$224.20	$224.20
7 purchase totals =	$939.27		$1,019.4414	$1,019.44	$1,019.45	$1,019.50