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	$209.85	7.349%	$225.2719	$225.27	$225.25	$225.30
Purchase #2	$181.61	13.378%	$205.9058	$205.91	$205.90	$205.90
Purchase #3	$46.33	9.269%	$50.6243	$50.62	$50.60	$50.60
Purchase #4	$92.55	8.192%	$100.1317	$100.13	$100.15	$100.10
Purchase #5	$196.71	9.476%	$215.3502	$215.35	$215.35	$215.40
Purchase #6	$55.52	4.389%	$57.9568	$57.96	$57.95	$58.00
Purchase #7	$154.73	10.552%	$171.0571	$171.06	$171.05	$171.10
7 purchase totals =	$937.30		$1,026.2978	$1,026.30	$1,026.25	$1,026.40