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	$77.70	4.309%	$81.0481	$81.05	$81.05	$81.00
Purchase #2	$188.37	3.135%	$194.2754	$194.28	$194.30	$194.30
Purchase #3	$135.41	12.279%	$152.037	$152.04	$152.05	$152.00
Purchase #4	$12.31	3.544%	$12.7463	$12.75	$12.75	$12.70
Purchase #5	$136.67	6.441%	$145.4729	$145.47	$145.45	$145.50
Purchase #6	$232.27	9.842%	$255.13	$255.13	$255.15	$255.10
Purchase #7	$166.72	5.229%	$175.4378	$175.44	$175.45	$175.40
7 purchase totals =	$949.45		$1,016.1475	$1,016.16	$1,016.20	$1,016.00