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	$9.67	4.824%	$10.1365	$10.14	$10.15	$10.10
Purchase #2	$219.32	8.659%	$238.3109	$238.31	$238.30	$238.30
Purchase #3	$59.81	3.281%	$61.7724	$61.77	$61.75	$61.80
Purchase #4	$27.81	3.740%	$28.8501	$28.85	$28.85	$28.90
Purchase #5	$232.77	5.466%	$245.4932	$245.49	$245.50	$245.50
Purchase #6	$239.75	9.833%	$263.3246	$263.32	$263.30	$263.30
Purchase #7	$79.27	13.541%	$90.004	$90.00	$90.00	$90.00
7 purchase totals =	$868.40		$937.8917	$937.88	$937.85	$937.90