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	$103.73	5.399%	$109.3304	$109.33	$109.35	$109.30
Purchase #2	$233.55	6.757%	$249.331	$249.33	$249.35	$249.30
Purchase #3	$239.61	10.309%	$264.3114	$264.31	$264.30	$264.30
Purchase #4	$174.88	9.459%	$191.4219	$191.42	$191.40	$191.40
Purchase #5	$50.91	5.458%	$53.6887	$53.69	$53.70	$53.70
Purchase #6	$87.71	4.760%	$91.885	$91.89	$91.90	$91.90
Purchase #7	$200.75	10.361%	$221.5497	$221.55	$221.55	$221.50
7 purchase totals =	$1,091.14		$1,181.5181	$1,181.52	$1,181.55	$1,181.40