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	$51.66	6.191%	$54.8583	$54.86	$54.85	$54.90
Purchase #2	$86.59	4.560%	$90.5385	$90.54	$90.55	$90.50
Purchase #3	$209.86	3.558%	$217.3268	$217.33	$217.35	$217.30
Purchase #4	$80.84	3.236%	$83.456	$83.46	$83.45	$83.50
Purchase #5	$235.67	13.431%	$267.3228	$267.32	$267.30	$267.30
Purchase #6	$65.41	8.616%	$71.0457	$71.05	$71.05	$71.00
Purchase #7	$197.64	9.552%	$216.5186	$216.52	$216.50	$216.50
7 purchase totals =	$927.67		$1,001.0667	$1,001.08	$1,001.05	$1,001.00