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	$181.82	4.214%	$189.4819	$189.48	$189.50	$189.50
Purchase #2	$73.75	11.113%	$81.9458	$81.95	$81.95	$81.90
Purchase #3	$106.32	11.392%	$118.432	$118.43	$118.45	$118.40
Purchase #4	$184.82	6.466%	$196.7705	$196.77	$196.75	$196.80
Purchase #5	$234.48	6.751%	$250.3097	$250.31	$250.30	$250.30
Purchase #6	$170.73	4.662%	$178.6894	$178.69	$178.70	$178.70
Purchase #7	$236.42	3.809%	$245.4252	$245.43	$245.45	$245.40
7 purchase totals =	$1,188.34		$1,261.0545	$1,261.06	$1,261.10	$1,261.00