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	$171.27	4.247%	$178.5438	$178.54	$178.55	$178.50
Purchase #2	$79.46	7.203%	$85.1835	$85.18	$85.20	$85.20
Purchase #3	$156.36	7.745%	$168.4701	$168.47	$168.45	$168.50
Purchase #4	$204.52	6.648%	$218.1165	$218.12	$218.10	$218.10
Purchase #5	$85.76	5.295%	$90.301	$90.30	$90.30	$90.30
Purchase #6	$229.89	6.444%	$244.7041	$244.70	$244.70	$244.70
Purchase #7	$41.68	6.372%	$44.3358	$44.34	$44.35	$44.30
7 purchase totals =	$968.94		$1,029.6548	$1,029.65	$1,029.65	$1,029.60