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	$90.64	4.611%	$94.8194	$94.82	$94.80	$94.80
Purchase #2	$81.35	9.727%	$89.2629	$89.26	$89.25	$89.30
Purchase #3	$121.83	6.121%	$129.2872	$129.29	$129.30	$129.30
Purchase #4	$33.89	11.867%	$37.9117	$37.91	$37.90	$37.90
Purchase #5	$205.92	12.169%	$230.9784	$230.98	$231.00	$231.00
Purchase #6	$114.33	5.320%	$120.4124	$120.41	$120.40	$120.40
Purchase #7	$136.55	7.746%	$147.1272	$147.13	$147.15	$147.10
7 purchase totals =	$784.51		$849.7992	$849.80	$849.80	$849.80